After some leaks on the web last week, the new 50mm standard-lens from Nikon is now reality with Amazon.com offering preorders for 218 USD. Nikonrumors is quoting an expected delivery date of June 16th, the German Nikon site says "beginning June" at 229 EUR (that would be incl. 18% VAT).
The lens looks like a larger copy of the 35/1.8G with added distance-window and one aspherical element. MTF-curve looks good, better than the AF-S 50/1.4G, but that was (almost) to be expected, as both lenses are measured wide open.
See more details of this lens over at Nikon-central.
If the optical construction and the price is anything to go by, I'd expect performance similar to the DX 35/1.8. And should I get my hands on a copy I'd certainly be testing for transmission too.

Now, let's have some side-by-side comparison of the new AF-S 50/1.8G, the DX AF-S 35/1.8G and the AF-S 50/1.4G

See the respective MTF-charts side-by-side:
...and remember that the DX-lens (middle) only covers a 14mm image circle, so for an apples-to-apples comparison you have to take the left half of the 50mm MTF-chart (up to 14mm)

Now for the respective cross-sections:
Pretty similar at the back-end, but the 50/1.8G has one less lens-element in the front-end.

An interesting tidbit from the technical data is the MFD (minimum focus distance) of 45cm and a max magnification of 1:6.7. This is not bad for a 50mm standard lens (actually the same as with the AF-S 50/1.4G)

Well,Canon officially lost all advantages of their systems for begineers,now that the AF-S 50 F/1.8 is out.(or soon will be) The Canon "Kinder Surprise" 50mm F/1.8 will atract less & less people,compared to these 2 sharper & better built lenses.

my prediction, performs better wide open, but no difference at around f/3.5 and higher. The only thing that might even be better is the AF-speed that will probably make the lens less accurate but people wanted a faster focussing 50mm

Poppies are such wonderful subjects for test-shots: Their stems have very fine hair!
Here are some first observations from comparisons side-by-side on a D300 DX body with the Nikon 50/1.4G seem under controlled conditions.

They seem to confirm what the MTF-Charts indicate: the new 1.8G lens is a little sharper/contrasty wide open than the 1.4G lens. At f/2.0 the differences are almost gone, that is you need some serious pixel-peeping to find any.

There might be a little bit more field curvature on the 1.8G but that can only be tested on flat targets.

Bokeh seems comparable between both lenses with the 1.4G perhaps a little more nervous in front of the focal plane. But again that is something that I'll have to specifically test for.

Transmission didn't show any obvious differences, but there is a real 2/3 stop advantage of the 1.4G and also the oof-blur is clearly stronger at f/1.4 than at f/1.8.

Here are both lenses wide open (f/1.8G 1st, f/1.4G 2nd), focus is on the center. Click through to large originals:
Nikon AF-S 50mm f/1.8G at f/1.8, 1/500, ISO 200

Nikon AF-S 50mm f/1.4G at f/1.4, 1/1000, ISO 200

So that's it for today. Please understand that these are preliminary findings from just one series of shots. I'll be off for Whitsun but will be reporting back as soon as I have more results.

The 50mm 1.8 does definitively seem to be sharper, but that's to be expected. The local camera shops are finally getting them in stock, I think that I'll be down there today testing out the two lenses.